Process and apparatus for false twisting synthetic yarns

ABSTRACT

A system is provided to false twist and simultaneously draw a linear synthetic high polymer yarn. The yarn is first heated and then false twisted in a novel false twister wherein the diameter of the twisting chamber is considerably greater than the yarn feeding and discharge channels.

United States Patent Leibbrand et al. 1 Dec. 19, 1972 PROCESS ANDAPPARATUS FOR [56] References Cited FALSE TWISTING SYNTHETIC YARNSUNITED STATES PATENTS [72] Inventors: Bertus Leibbrand, Elst; Johan J. 3079 745 311963 B t I 57177 3 x reen e a 21:??? figzis iih gz' g'2,515,299 7/1950 Foster et al ..s7/77.3 A E L d A d 2,863,280 12/1958Ubbelohde ....57/77.3 x m e 3,022,566 2/1962 Daniels et al. ..57/34 BArnhem of Netherlands 3,206,922 9/1965 Nagahara et 8].... .....57/34 HSx [73] Assignee: Akzona incorporated, Ashevme 3,237,392 3/1966 Crouzet..57/34 HS X N.C. Primary Examiner-Donald E. Watkins [22] Flledz Oct. 8,1970 Attorney-Albin F. Knight 21 A 1. No.1 79 231 1 pp 57 ABSTRACT [30]Foreign Application Priority Data A system is provided to t'alse twistand simultaneously draw a lmear synthetic high polymer yam. The yarn isOct. 14, 1969 Netherlands ..69l5479 fi t heated and then f l twisted ina novel f l 1969 Netherlands twister wherein the diameter of thetwisting chamber Oct. 14, 1969 Netherlands ....691548] is considerablygreater than the yam f di and Oct. 14, Netherlands discharge channels[52] U.S. CI. ..57/34 HS, 57/34 B, 57/77.3,

57/157 TS, 57/157 F [51] 1m. (:1 ..D02g l/16, D02g 1/02 11 C 1 DrawmgFigures [58] Field of Search.57[ 34 R, 34 HS, 51, 77.3,77.45,

PATENTEDBEB 1' W2 3.706.192 sum 1 or 2 L L .l

20 1 INVENTORS BERTUS LEIBRAND JOHAN J. MERTENS HARM A. PLOEGER ROBERTSLUI JTERS LEENDERT van ASSENDELFT ATTORNEY PKTENTED 19 I97? 3. 708. 192

sum 2 BF 2 FIG. 3

I8 [16 17 29 72:41 Ei t EEE 2 23 H 24 INVENTORS BERTUS LEIBRAND JOHAN J.MERTENS HARM A. PLOEGER ROBERT SLUIJTERS LEENDERT van ASSENDELFT Mi-MATTORNEY PROCESS AND APPARATUS FOR FALSE TWISTING SYNTHETIC YARNS Thepresent invention relates to a process and apparatus for false twistingsynthetic linear high polymer yarns, threads and the like. Moreparticularly, the invention relates to an improved system for falsetwisting yarn in pneumatic jets while drawing the same to several timesits original length.

Apparatus of this general type is known in the art but has not beencommercially satisfactory. The systems used did not give the yarn asufficiently high angular velocity to obtain in the yarn a temporarytwist of the high level required. This was found to be particularly trueas the trend in the industry was to the application of ever increasinglinear speeds of the yarn.

US. Pat. Nos. 3,009,309; 3,069,836, and 3,206,922 all disclose pneumaticjets for imparting a false twist to the yarn. However, in each case theyarn is twisted after the drawing operation and under a decreasedtension or let-off in order to produce a crimped or bulked yarn.

It is therefore an object of the present invention to overcome theshortcomings and deficiencies in the prior art.

It is a further object to provide a system for producing a false twistedyarn that is stable, compact, and of high quality for use in theknitting and weaving trades.

Another object is to correlate the several elements in the system toprovide an improved process.

Still another object is the provision of a unique false twistingapparatus.

These and other objects and advantages will become apparent whenconsidered in conjunction with the accompanying drawings wherein:

FIG. 1 shows a schematic view of an improved arrangement of apparatusfor carrying out the process of the invention as a continuous operation;

FIG. 2 is an enlarged sectional view of the pneumatic false twister;

FIG. 3 is a modified version of FIG. 1; and

FIG. 4 shows an enlarged -modified section of the pneumatic chamber withportions of the channels shown on each end of the chamber.

Referring now to the drawings, undrawn yarn is conveyed from a supplypackage 11 via pigtail guide 12 to a pair of constant-speed feed rolls13. The yarn is then passed to a hot pin 14 heated to about 140 C. andmakes at least one wrap therearound and after passing around the hot pinis led through a tubular oven 15 of from 2 to 3 meters in length andheated to a temperature of about 175 C. The oven 15 is surrounded by asteam jacket 16.

After leaving the oven 15, the yarn is passed through an openingprovided in a baffle 17 and then enters a pneumatic false twistergenerally shown at 18, an enlarged view of which is shown in FIG. 2.

The pneumatic false twister 18 consists of a substantially cylindricalchamber 19 into which compressed air is blown in a tangential directionthrough a slot 20 via air inlet 21 At one end of chamber 19 there isdisposed a yarn feed channel 22 and at the other end of the chamber adischarge channel 23. The yarn feed and discharge channels are of equallength, which length L is of from 25 to 150 times as large as theirinside diameter d. The length L may, for instance, be 25, 50, 75, 100,125 to 150 times as large as the diameter d. It is preferred that theinside diameter D of the chamber is at least approximately 1.2 to 1.5times the inside diameter d of the feed and discharge channels 22 and23.

On the inside of, and adjacent to, the chamber 19 the connections tochannels 22 and 23 are. suitably rounded off. The baffle l7 is locatedat an adjustable distance from feed channel 22.

After leaving false twister 18, the yarn passes on to a draw roll 24provided with separator roll 25. Depending on the desired draw ratio ofthe yarn, the circumferential velocity of the draw roll may be chosen tobe, for instance, 1.5 to 4 times that of feed rolls 13. Finally, thedrawn and false twisted yarn 26, after passing through a top pigtailguide 27, is taken up on a ring twister 28.

The adjustable distance A between feed channel 22 and oven 15 is notmore than approximately 250 mm., but preferably between 20 to 35 mm. Thebaffle 17 is located at an adjustable distance B from feed channel 22.

The embodiment according to FIG. 3 differs from that according to FIG. 1in that downstream of the pneumatic false twister l8 and at somedistance therefrom there is provided a second mechanical false twister29. The second false twister 29 may be constructed in different waysknown in the art and is therefore represented in the drawing onlyschematically. After the yarn has left the second false twister 29, itpasses on to a roll 24 with separator roll 25 FIG. 4 is a partial viewof a modified embodiment of a false twister, like parts being indicatedby like numerals. Near the end of the yarn inlet side, the wall ofchamber 19 is provided with an annular zone 30 whose diameter is largerthan that of the adjoining wall portion of chamber 19. Via a narrow slit31 the annular zone 30 connects with a collecting space 32 whichcommunicates with the ambient air via a channel 33. Under the influenceof the centrifugal force, dust, for instance in the form of titaniumdioxide, coming from the yarn will be forced into the collecting space32, from where it will be discharged into the ambient atmosphere viachannel 33.

By the use of the foregoing apparatus according to the invention, it ispossible to give the yarn an angular velocity of as high as a fewmillion revolutions per minute. This makes it possible to give the yarna temporary twist, that is, a false twist, of customary level, incombination with a yarn transport velocity of from 300 to 800 meters perminute, which velocity is very high for a false twisting process.

By way of example, the apparatus according to the invention was used forthe false twisting of a six-filament polyamide yarn having a totaldenier of 20. While traveling at a speed of 700 meters per minute, theyarn was, in the pneumatic false twisting device, caused to rotate at arate of 3.5 million revolutions per minute. This led. to the formationin the yarn of a temporary twist, or false twist, of the order of 3.5 X10 /700 5000 turns per meter.

the circumference thereof and in tangential direction, escapes to thesurrounding atmosphere through the coaxial feed and discharge channelsprovided at the end surfaces of chamber. The feed and discharge channelshave a much smaller diameter than the chamber, so that the velocity ofrotation of the air is increased considerably as it enters the feed anddischarge channels.

Since the inside diameter of the feed and discharge channels isconsiderably larger than the diameter of the yarn to be treated, whichmay have a denier of, say 20, the rolling of the yarn against the insideof the channels takes place at a high transmission ratio, which isanother factor contributing to a high rotational velocity of the yarn.

In spite of the high rotational velocities, the process can readily bestarted andkept running smoothly if the apparatus is further equippedwith a second false twister downstream of the pneumatic first falsetwister. In other words, there is provided another mechanical falsetwister which serves to impart to the yarn at least 5 to percent, moreparticularly 30 to 40 percent, of the total amount of twist temporarilypresent in the yarn. The 'apparatus,.according to the invention, hasadvantage in that said mechanical false twister is formed by a drivenfalse twisting spindle or a friction disc, or a yam-wrapped rotatingroller or tube whose longitudinal axis is at an angle with thelongitudinal direction of the yarn.

High speeds required for economic reasons can be applied and the correctdraw ration be chosen which is necessary to finallyobtain a yarn of aparticular denier if the apparatus according to the invention locatesboth the pneumatic first false twister and the second false twisterbetween the feed rolls and the draw rolls.

With the false twisting apparatus, the yarn is, in a known manner,successively heated upstream of the pneumatic twister and cooled.

The cooling is effected in such a manner that after leaving the heatingmember the yarn is over a relatively long distance, say 400 to 500 mm.,passed through the ambient air before it'arrives at the false twister.

In known apparatus the very high economic valve of the yarn speedbecause of the combination with the drawing process will call for aneven longer cooling zone between the heating member and the falsetwisting member, which is difficult to realize because of the availableheight and space.

According to the present invention, the false twisting apparatus isunique in that the distance between the pneumatic false twister and theheating member is not more than approximately 250 mm. With a preferredembodiment of the apparatus according to the invention, the distancebetween the pneumatic false twister and the heating member isapproximately to 35 mm. Despite the short length of the cooling zonebetween the false twister andthe heating member, it has surprisinglybeen found that even at speeds of from 500 to 1,000 meters per minute,which are uncommonly high for false twisting processes, the apparatusaccording to the invention provides a satisfactory cooling and that alonger cooling zone even has an adverse influence on the quality of theyarn. In a preferred embodiment of the apparatus according to theinvention, the distance member is adjustable.

The results obtained with the apparatus, according to the invention, canbe improved in a simple manner by disposing a shield or baffle betweenthe pneumatic false twister and the heating member. This shield isprovided with an opening for passage of the yarn and protects the yarnagainst the heat on one side and air on the other. An efficaciousconstruction is also obtained if the apparatus is constructed so thatthe longitudinal axes of the yarn feed channel of the pneumatic falsetwister and the heating member are not positioned coaxially.

Internal wear of the pneumatic false twister can be inhibited if at ornear the circumference of the chamber wall of the pneumatic falsetwister, on its inside it is locally provided with a narrow dischargeopening. According to the invention, the narrow discharge opening hasthe advantage that in the annular zone the diameter is greater than thatof the adjoining portion of between the pneumatic false twister and theheating the chamber wall. In a preferred embodiment of the apparatus,the narrow discharge opening connects with a collecting space which islocated at a larger radial distance from the center of the chamber, thecollecting space being in open communication with the ambient atmospherevia a narrow channel.

It is preferred that the annular zone should be formed at the yarn inletside of the chamber. It surprisingly has been found that in spite of thehigh air velocities, the internal wear of the pneumatic false twisteraccording to the invention is negligibly small, which is probably to beattributed to the face that under the influence of the centrifugalforces the hard particles, such as titanium dioxide, coming from theyarn, collect in the annular zone of relatively large diameter fromwhere they are discharged into the ambient atmosphere.

What is claimed is:

1. Apparatus for false twisting synthetic yarns which comprises yamfeeding means and yarn drawing means for transporting the yarn from asource of supply to a take-up device, a pneumatic false twister formedwith a cylindrical chamber and provided with means to supply compressedair in a tangential direction along the circumference of the chamber,feed and discharge channels rigidly mounted on each end of the chamber,the inside diameter of the chamber being substantially greater than theinside diameter of the channels, and the length of each channel being atleast 10 times that of their inside diameter.

2. Apparatus according to claim 1 in which the inside diameter of thechamber is at least 1.2 to 1.5 times the inside diameter of the feed anddischarge channels.

3. Apparatus according to claim 1 in which the length of the feed anddischarge channels is 25 to times that of their inside diameter.

4. Apparatus according to claim 1 which further comprises a mechanicalfalse twister disposed downstream of the pneumatic false twister.

5. Apparatus according to claim 4 in which the pneumatic false twisterand the mechanical false twister are both located between the yarnfeeding means and the yarn drawing means.

6. Apparatus according to claim 1 which further comprises heating meansdisposed between the yarn feeding means and the false twister.

7. Apparatus according to claim 6 in which the distance between thepneumatic false twister and the heating means is approximately 20-35 mm.

8. Apparatus according to claim 1 which further comprises a shield orbaffle disposed between the pneumatic false twister and the heatingmeans to provide passage for the yarn.

9. Apparatus according to claim 1 which further 5 comprises a narrowdischarge opening at or near the circumference of the chamber wall ofthe pneumatic false twister.

10. Apparatus according to claim 9 in which the narrow discharge openingis connected to a collecting 10 space located at a larger radialdistance from the center of the chamber, the collecting space being inopen

1. Apparatus for false twisting synthetic yarns which comprises yarnfeeding means and yarn drawing means for transporting the yarn from asource of supply to a take-up device, a pneumatic false twister formedwith a cylindrical chamber and provided with means to supply compressedair in a tangential direction along the circumference of the chamber,feed and discharge channels rigidly mounted on each end of the chamber,the inside diameter of the chamber being substantially greater than theinside diameter of the channels, and the length of each channel being atleast 10 times that of their inside diameter.
 2. Apparatus according toclaim 1 in which the inside diameter of the chamber is at least 1.2 to1.5 times the inside diameter of the feed and discharge channels. 3.Apparatus according to claim 1 in which the length of the feed anddischarge channels is 25 to 150 times that of their inside diameter. 4.Apparatus according to claim 1 which further comprises a mechanicalfalse twister disposed downstream of the pneumatic false twister. 5.Apparatus according to claim 4 in which the pneumatic false twister andthe mechanical false twister are both located between the yarn feedingmeans and the yarn drawing means.
 6. Apparatus according to claim 1which further comprises heating means disposed between the yarn feedingmeans and the false twister.
 7. Apparatus according to claim 6 in whichthe distance between the pneumatic false twister and the heating meansis approximately 20-35 mm.
 8. Apparatus according to claim 1 whichfurther comprises a shield or baffle disposed between the pneumaticfalse twister and the heating means to provide passage for the yarn. 9.Apparatus according to claim 1 which further comprises a narrowdischarge opening at or near the circumference of the chamber wall ofthe pneumatic false twister.
 10. Apparatus according to claim 9 in whichthe narrow discharge opening is connected to a collecting space locatedat a larger radial distance from the center of the chamber, thecollecting space being in open communication with the ambient atmospherevia the narrow discharge opening.
 11. A process for treatment ofsynthetic yarn while transporting yarn from a source of yarn supplythrough a drawing zone to a collection zone, comprising the steps ofsequentially heating, cooling and false twisting the yarn in the drawingzone, the false twisting being achieved by forming a forced vortex ofair around the yarn and increasing the angular velocity of rotation ofthe forced vortex.